This application claims the priority of German application 198 47 159.9, filed in Germany on Oct. 13, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a compressor for producing oil-free compressed air, with a transmission driven by a drive shaft, provided with a swash plate, and lubricated by oil, said transmission being connected by piston rods with pistons that act alternately against an oil-cooled cylinder head, with oil that serves to cool a pressure side of the compressor also being used to lubricate a transmission side.
Compressors of the above-noted type such as described in German Patent Document No. DE 197 06 066 A1 are especially suited for installation in motor vehicles. Provision is made for connecting the compressor to the lubricating oil and coolant circuits of the vehicle engine. However, in view of the high loads on vehicle engines and the fact that the maintenance of these media is not always guaranteed, it is not always advantageous for the compressor to be connected to these circuits. The cooling water and the lubricating oil are considerably heated by the engine. As a result, the cooling effect on the compressor is often very small. In addition, because it is installed in the immediate vicinity of the vehicle engine, the compressor is exposed to the heat radiated from the engine. Dry-running piston rings made of plastic are used in compressors to produce oil-free compressed air. Good cooling, however, is of critical importance for the service life of these piston rings.
Hence, a goal of the invention is to improve a compressor of the above-noted type species so that the heat is carried away from the hot zones into areas that are subject to less heat stress. It should also be possible to drive the compressor separately from the drive of a main drive, preferably by using a separate electric motor in such fashion that the compressor can be used universally. In particular, cooling should be provided such that production of oil-free compressed air remains guaranteed when using piston rings made of plastic.
According to the invention, the goal is achieved by providing a compressor of the above-noted type, wherein the oil that serves to cool and lubricate is specified by a quantity of oil that is encapsulated and permanent and is located inside a compressor housing, wherein an interior of the compressor is divided by check valves into a pressure area that surrounds the cylinder head and the piston arrangement, and a transmission area that contains the drive shaft and the swash plate, and wherein a delivery device is provided that pumps the oil depending on the flow direction specified by the check valves in a circuit between the pressure area and the transmission area.
By using a separate permanent lubricating oil and cooling oil circuit, the compressor can be located at any point in a vehicle for example; in this case, the compressor is driven by an electric motor. This in turn has the advantage that the compressor delivers a constant power independently of the rotational speed of the vehicle engine. In addition, the compressor can be started before the vehicle engine is started. This is advantageous when it is desirable for the vehicle to reach operating readiness quickly.
Integrated lubricating oil and cooling oil supply make the compressor especially suited even for installation in stationary air supply systems. The type of cooling with an encapsulated design for the compressor makes it possible to use plastic for important parts: This applies in particular to housing parts which can be clamped sandwich-fashion between the transmission area and the cylinder head.
Advantageous features of preferred embodiments of the invention are described herein and in the claims.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.